Ultra high speed dental type handpiece instruments are conventionally configured in two major configurations. In one configuration the bur is aligned in a straight line with the dental instrument's handle. This configuration is used in dental laboratories for shaping anatomy and can also be used by wood carvers, glass engravers and other arts and craft users. It is not used in the oral cavity.
In the second configuration, used by dentists within the oral cavity, called a contra angle handpiece, the cutting bur is angled sharply with respect to the handle. This angled mounting of the bur is necessary for the user to reach the top and bottom of a tooth structure. Other features the second configurations may have over those in the first configuration include fiber optics, and chip air and water lines to cool the tooth.
The present invention discloses a new handpiece design which is similar to the first configuration, or laboratory style instrument, but differs by the way a turbine which is powered by the routing of input and exhaust gases. The inputted air is directly supplied to the front of the instrument near its bur head, rather than through or near the rear handle. In addition, the exhaust gas is not routed through the handle. By using a short length of PVC (polyvinyl chloride) tubing pinched closed at one end and mounted on the front end of the instrument near the bur, several advantages are achieved.
One of the advantages is lubrication. In conventional designs lubrication is fed to the turbine by removing the input tubing from the handpiece and applying oil into the tubing resulting in most of the lubrication blowing out, without touching the internal bearings. In the present invention,. an aerosol lubricator, similar to WD40 .TM. is used by squeezing an exhaust port with the fingers to make the tubing round and then inserting the aerosol tip into the exhaust stack while pressing the plunger once. This applies a metered amount of lubrication directly into the turbine bearings, saturating them. Using a pinched end for the exhaust stack also has the added advantage of preventing dirt from entering the turbine housing should the handpiece be laid down in dirt.
Still another advantage of using a pinched exhaust stack relates to an inherent problem in ultra high speed dental type instruments. As compressed gas.is used to power the instrument and there is positive air pressure existing in the instrument, there is no chance that dirt will enter the turbine housing. However, when the compressed gas supply is removed, the handpiece turbine continues to spin for several seconds as a result of momentum. During this time the spinning action becomes a vacuum pump and pulls contaminated air up the spindle, directly into the front bearing. For this reason dental handpieces need to be autoclaved to kill any biological matter that might have entered the turbine housing during its shut down operation. In the present invention, the pinched exhaust stack tubing causes the drive air pressure to decline slowly as it also closes the exhaust port to prevent the described vacuum pump phenomenon called "suck up".
Details of the construction and operation of the present invention are described hereafter.